The physicist of the floating frog also has a Nobel

At the High Field Magnet Laboratory of the University of Nijmegen, in the Netherlands, the physicist Andre Geim had a live frog hanging in mid-air one Friday in 1997, inside the bore of a 16-tesla magnet: roughly 300,000 times the Earth's magnetic field. The frog was not tied to anything. Thirteen years later, the same man collected the Nobel Prize in Physics in Stockholm.

The frog business began with tap water. Geim wanted to see what a stream of water would do falling through the magnet's bore, so he poured some in and leaned over to look. The water did not fall: it hung halfway down, a trembling ball that neither dropped nor rose. Then came the hazelnuts, the flowers, a grasshopper. The frog was suggested by Irina Grigorieva, a physicist in the same laboratory and Geim's wife, on a simple argument: a frog is eighty per cent water. The frog rose to the centre of the magnet, stayed up there, and went on paddling its legs like something swimming, because from its own point of view it was swimming. When they switched off the field it came down by itself and went back to its tank without a scratch.

The effect is called diamagnetic levitation. Every material responds slightly the wrong way round when it enters a magnetic field —iron does too, it is just that a far stronger response buries it—: water turns into a tiny magnet of the opposite sign, so the field pushes it towards wherever the field is weakest. The push is ridiculous. So ridiculous that for a century and a half it was written off as useless: the Dutchman Anton Brugmans saw in 1778 that a piece of bismuth edged away from a magnet, and in 1845 Michael Faraday described it in detail and adopted for it the word William Whewell had suggested, which it still carries. What arrived in the nineties were magnets capable of 16 teslas. At 16 teslas that ridiculous push ends up equalling exactly what the frog weighs, and then the frog has no reason at all to fall.

In 2000, Geim and the British physicist Michael Berry, his co-author on the paper in the European Journal of Physics, were given the Ig Nobel Prize in Physics: an award handed out every autumn in the United States for genuine research that looks like a joke. Geim travelled to Harvard to collect it. Berry had a prior commitment that day and could not go.

Four years later, now at the University of Manchester, Geim and his colleague Konstantin Novoselov pressed a strip of sticky tape onto a block of graphite —the stuff inside a pencil lead— and pulled. Left on the tape were sheets of carbon one atom thick: graphene, the material theory said could not be obtained on its own. It came out of the sessions Geim called Friday night experiments, which he had already been running back in Nijmegen: the evenings when everyone had to work on something outside their own field. The frog came out of one of those nights in Nijmegen. Graphene came out of another in Manchester. The 2010 Nobel was for graphene, and with it Geim became the first person to win both prizes as an individual.

In the Ig Nobel citation for 2000 the reason fits on one line: for using magnets to levitate a frog. The Stockholm citation needs two paragraphs of solid-state physics. And even so, of the two, the hard experiment was the frog. Graphite stays where you put it.